1. Field of the Invention
This invention relates to a fluid pressure intensifier device and more particularly, although not exclusively, to a device for intensifying gas pressure.
2. Description of the Prior Art
Compressed air stored in a pressure vessel finds particular use for power and control in systems that require a short burst of high level power, especially when the system requires stored energy. For high release rates, an air accumulator is an order of magnitude lighter than electric batteries, and much lighter than an hydraulic accumulator. Furthermore, the air operated system can operate over a much wider range of hot and cold temperatures.
Thus, compressed air may find a number of uses in aircraft applications including, for example, operation of brakes and landing gear, whilst being particularly useful for starting engines or auxiliary power units because this operation requires stored energy, high power level and cold operation.
Pressurised nitrogen is frequently used in a nitrogen inerting system to pressurise aircraft fuel tanks and, in modern day aircraft, the nitrogen source may be low pressure nitrogen delivered by a molecular sieve type gas separation system and subsequently pressure intensified.
Similarly, oxygen-enriched air for breathing by aircrew is now frequently supplied by a molecular sieve gas separation system which delivers the oxygen-enriched air at low pressure so that pressure intensification may be a requirement.
There is a requirement, therefore, in aircraft and in other applications, for a compressor or pressure intensifier device suitable for intensifying the pressure of a range of gases including air.
Most of the air compressors or pressure intensifier devices presently available are old in design and do not meet the requirements of modern aircraft with respect to life, reliability and weight. There is a clear need for an improved pressure intensifier device capable of satisfying the potential applications hereinbefore mentioned.
U.S. Pat. No. 4,516,913 discloses a multi-stage drum compressor having a plurality of piston and cylinder stages of different volume angularly spaced at locations around a longitudinal axis of the drum. The first piston and cylinder stage has the largest volume and subsequent stages are of decreasing volume with the last stage having the smallest volume. The stages are interconnected by passages provided in the drum for conducting gas to be compressed sequentially to each of the stages. The pistons of the stages are actuated by a shaft driven swash plate. This mechanism is a source of significant wear and tear because it functions to transfer forces from the rotating shaft to the pistons, and from one piston to another. Also, because the cylinder side walls are marginally lubricated, piston side loads are particularly troublesome causing premature wear-out.